Suppose you have a apache httpd server working as a reverse proxy. Now suppose that this server has to set a HTTP request header called “token” to be attached to every request made to the backends, and that the header’s value must be copied from a query string parameter called “querytoken”.

What it follows is a quick n’ dirty but working list of things to do to correctly install you brand new courier mta mail server from source on a linux debian system (or ubuntu). This is for the impatients that don’t want to read the courier installation manual page (http://www.courier-mta.org/install.html). You can download the last stable courier packages from here: http://www.courier-mta.org/download.php.
You only have to download those three software archive files:

Courier

Courier authentication library

Courier unicode library

You’ll need to be root and have an internet connection to install dependencies debian packages.
First of all you have to enable the EN_US-utf8 locale, or “make check” will fail. You can do it with:

make
make check
exit
make install-strip
make install-configure >upgrade.log

/opt/courier/sbin/showmodules
/opt/courier/sbin/makesmtpaccess

OK. If everything gone OK, the installation stuff was terminated.
The configuration stuff is another complex thing that I cannot cover now here… may be another time.
Now, continue to read installation manual from here: http://www.courier-mta.org/install.html#aliases

This procedure was last tested with courier 0.75.0 on debian 8.4, but should be OK with newer versions too.
The software will be installed in /opt/courier.